Comets formed in circular orbits but were gravitationally flung into their present-day elliptical orbits when they ventured too close to planets.
彗星在圆形轨道上形成，但当它们冒险太接近行星时，就会被引力抛入现在的椭圆轨道。
The nearly circular orbits of planets in our solar system led scientists to expect that planets around other stars would also reside in circular orbits.
在我们的太阳系中，行星的轨道几乎是圆形的，这使得科学家们预测，其他恒星周围的行星也会位于圆形轨道上。
Now, circular orbits are special.
圆形轨道非常特殊。
Let's pursue the idea of circular orbits.
我们用圆轨道的概念。
Like the solar system, the planets orbiting Gliese 581 have mostly circular orbits.
和太阳系一样，围绕着Gliese 581运行的行星轨道大部分都是圆形的。
Like our solar system, the planets around Gliese 581 have nearly-circular orbits.
Gliese 581周围的行星拥有同太阳系的行星一样类圆形轨道。
Kepler's 3rd law for circular orbits; Building up the shell-force by integration; Spring gun.
开普勒圆周轨道第三定律；利用积分推导球壳的引力；弹簧。
Later in the course, we will cover elliptical orbits, but now let's exclusively talk about circular orbits.
我们在之后的课程还会讲到椭圆轨道，不过现在我们只讲，圆轨道。
Most of application satellites are running in near circular orbits, and many of them need to be controlled.
应用卫星绝大部分都是近圆轨道的卫星 ，其中又有很多是需要进行轨道控制的。
In his new paper, Dokuchaev has looked at stable circular orbits as well as spherical, non-equatorial orbits for photons at the inner boundary.
在Dokuchaev的这篇新论文里，他既考虑了光子在内边界的稳定圆轨道，也考虑了球形非赤道面轨道。
Based on the two-body assumption, two methods are used to investigate the relative motion of satellite formation flying on circular or near-circular orbits.
首先基于二体假设，采用两种方法系统地研究了圆或近圆轨道上卫星编队飞行的相对运动。
Abstract: in order to reduce the cost of on-orbit service, the programming of on-orbit service mission for multiple object spacecraft in coplanar circular orbits was studied.
摘要为了降低“一对多”在轨服务的成本，以共面圆轨道卫星群为研究对象，开展了在轨服务任务规划问题的研究。
The optimal scheme is given for the dual-tangential transfer between two circular orbits by dual impulse method. The orbit perturbation as a result of the Earth's flattening is considered.
本文用两次冲量法给出了沿双共切椭圆轨道实现从一圆轨道向另一圆轨道转移的最优方案，并考虑到地球扁率造成的轨道摄动。
Most known extrasolar planets reside in highly elongated, not circular, orbits.
大多数已知的太阳系外行星都居住在高度拉长而非圆形的轨道上。
Let us just assume for simplicity now that the orbits are roughly circular just to get a little bit of feeling for it.
现在为了简便，暂且认为轨道均大致为圆形，大致熟悉一下。
Then, emphasis is placed on circular and projected circular flying-around orbits.
然后，重点讨论了空间圆和当地水平面投影圆两种绕飞轨道。
Then, emphasis is placed on circular and projected circular flying-around orbits.
然后，重点讨论了空间圆和当地水平面投影圆两种绕飞轨道。
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